Scavenging two-cycle internal combustion engine



F sAss ET AL 1, SGAVENGING TWO-CYCLE INTERNAL COMBUSTION ENGINE Filed Feb. 2:, 1928 Nov. 24, 1931,

Patented Nov. 24, 1931 UNITED STATES PATENT: OFFICE FRIEDRICH SASS, F IBERLIN-OHABLOTTENBUBG, JOHANNES RADLOFF, OF AND JOHANN GERSTMIAYR, OF IBERLIN-CEARLOTTENBURG, GERMANY, ABSIGNOR8 '10 ALLGEMEINE ELEKTBIGITATS-GESFLLSCHAIT, OF BERLIN, GERMANY .SGAVENGING TWO-CY OLE IN'I'EBNAL CO MBUS TION GINE Application filed February 28, 1928, Serial Ro.'256,310, and in Germany February 28, 1927.

Our invention relates to the scavenging of internal combustion engines. It is an ob ect of our invention .to provide scavenging means I in which whirling movementis imparted to the gases and all residues of exhaust gas in the cylinder are practically removed.

To this end we provide scavenging portsor passages which are so pro ortioned and mclined tangentially and axlally with respect 10 to the cylinder that the entire cylinder space is swept uniformly by the scavenging air. A whirling motion results from this arrangement of the ports or passages because the helical movement of the air particles'which prevails at the lower dead centre is, on the upward stroke of the piston, gradually deformed into a spiral and finally becomes circular. When this point is reached, fuel is injected, preferably by means of a plurality of separate jets at uniform angular pitch so that the fuel is uniformlydistributed in the compression chamber.

In internal combustion engines having port scavenging the efliciency of the scavenging is a function of its thoroughness. It is de-' sirable that no residues of exhaust gases should remain in the cylinder after scavenging. When the inlet and outlet ports for the scavenging air are at oppositeends of 3c the cylinder, an eflicient scavenging is readily attained, but when the inlet and outlet ports are arranged at the same end of the cylinder the problem becomes more difiicult. Heretofore in engines of the latter type, the scavenging air flowed principally along the inner walls of the cylinder, leaving in the cylinder a core of exhaust gas which was not entrained by the scavenging air. In order to overcome this drawback'it has lo been suggested to conduct the scavenging air from the inlet ports toward the axis of the cylinderso that it was deflected toward'the walls of the cylinder at the upper end of the cylinder and flowed down toward the outlet L5 ports along-the cylinder walls. The converse arrangement has also been proposed, but both these methods are not satisfactory as they still leave a'h'ollow cylindrical space between the upward flow in the axis and the downward i0 flow along the walls of the cylinder which.

an angle of about 360 degrees around the axis space is not permeated by the scaven ng air. This drawback cannot be eliminatedhy caus- Iiing mere whirling movement of the central ow.

It has also been attempted to generate a plurality of variously directed streams of scavenging air by suitably inclining the inlet ports on one side of the cylinder, the streams issuing from the several ports travelling through the cylinder in paths of different length before escaping from the outlet ports on the opposite side of the cylinder. With this method the central regions of the cylinder but not the regions at its walls are permeated by the scavenging air, so that this method is also imperfect;

These drawbacks are overcome, according to our invention, by so arranging the ports that the streams of scaven g air rise at an angle to the axis of the cylinder along a helical line, being first conductedtoward the axis ofthe cylinder and then deflected toward the angles at the cylinder cover. The air flows in a loop and at the same time rotates through of the cylinder so that the cylinder volume is thoroughly swept by the scavenging air. This can be concluded from the fact that the path of the air particles is much longer than in any other existing method, owing to the combined loop and helical movements.

In the drawings afixed to this specification and forming part thereof cylinders of twocycle internal combustion engines embodying our invention are illustrated diagrammatically by way of example.

In the drawings Fig. 1 is an axial section of a cylinder hav'-- ing the inlet and outlet ports for the scaveng ing air distributed over an angle of 180 degrees each on opposite sides of the cylinder, FFig. 2 is a section 'on the line II- -II in Fig, 3 is a section on the line AB in Fig. 2, 1

- Fig. 4 is a cross-section of a cylinder in which the inlet ports are arranged at a somewhat lower level than the outlet orts,-and' the two sets of ports are arranged in overlappingerelation, Fig. 5 is a section on the The passage 6 to which the several ports e are connected, is inclined upwardly at an angle a with respect to the head of the piston and the ports 0' are so arranged that the horizontal projections of their axes are tangents to a circle the diameter d of which is small as compared with the inside diameter of the cylinder a. Figs. 2 and 5 illustrate the flow of a particle of air fromone of the inlet ports 6' to one of the exhaust ports f. The particle leaves the port e at 1, first moves in a straight line as far as the circle (1, and then upwards in a slightly against the cylinder wall at 2. Atthis point it is gradually deflected tangentially whilerising to the point 3 below the cylinder top. While moving in this path the tangential component imparted to the particle is still active and causesthe article to flow in a chord 3, 4 below the cyiin it moves downwardly along the cylinder wall for some distance and finally is deflected into the exhaust port f on a substantially helical line 4, 5. In this manner each particle moves in a loop while at the about the axis of the cylinder. Finallythe gas is discharged through the outlet ports f which are connected with an inclined passage as will appear from Fig. 1. The outlet ports also extend over an angle of about 180' degrees opposite the inlet ports a, as shown in F' Obviously the scavenging ports or each set of them, that is the inlet and outlet ports, might extend over a larger or smaller part of the cylinder than corresponds to 180 degrees and the inlet or the exhaust ports, or both, might be arranged otherwise than radially.

Referring now to Figs. 4 and 5, the arrangement of inlet and outlet ports 6' and f is the same, each set extending over an angle of 180 degrees, but the sets are arranged at diflferent levels and in overlapping relation which requires staggering of the passages e and f. The relative position of the sets corresponds to an angle of 270 degrees.

By arranging the portsvat. various levels and by staggering be arranged for a cylinder of given diameter than with the ports at the same level as in this case the limiting angle for either set is 180 degs.

ais acylinder,

ment of the scavenging air,

curved line until it impinges der top whereupon same time rotating 7 them it is obvious that a in Figs. 4.- and 5 but that the sets may be over-' lapped as desired.

By our arrangement of ports the volume of air and gas in the cylinder is rotated throughout the cylinder space without undue resistance. Therotary movement of the particles occurs along a helical line when the piston b is at its lower dead centre, as shown, but the helix angle is-reduced gradually while the piston upper dead centre. upper dead centre into a spiral and along circular paths.

In the vicinity of the finally the particles move This circular movewhich now plays the roleof combustion air, is very important for complete combustion and indispensable for solid injection, and it will therefore be understood that our method of' imparting the described movement to the scavenging air is also very important from the point of view of complete combustion.

Various changes may be made in the deis moving toward the the curve is flattened out tails disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

We claim 1. A two-cycle internal combustion engine having a cylinder, and scavenging and exhaust ports in. said cylinder in the vicinity of its lower dead center position, the axes of "said scavenging ports being arranged at an angle to the transverse axis of the cylinder such that the diameter of the circle to,which the axes of the scavenging ports are tangent is small compared to the inside diameter of the cylinder, and said scavening ports being inclined to the vertical axis of the cylinder.

at an angle such that the scavening air currents pass through the cylinder space upward at an angle in a direction located between the radial and tangential planes such that they strike the opposite cylinder wall above its center and flow along the wall of the cylinder in a helical line up to the cylinder cover after which they cross the cylinder cover in the direction of a chord and then flow downward along the cylinder wall to the eZhaust poll-ts. l b

2. two-cyc e terna com ustion' en e having a cylindet gm ports in said cylinder in the vicinity of its lower dead' center position, characterized by the. fact that the scavenging ports are arranged tangentially with respect to the transverse axis of the cylinder at an angle circles the cylinder axis.

, and scavening and exhaust 3. A two-cycle internal combustion engine having a cylinder, and scavenging and exhaust'ports in said cylinder in the vicinity .of itslower dead center sition, said scavenging ports being inchned upwardly toward the head of the cylinder at an'angle such that their center lines meet the oppos te cylinder wall above the center of the region covered b the piston stroke and being at an angle wit respect to the transverse axis of the. cylinder such that their center lines are tangent to a circle less than one-third the diameter of the cylinder. In testimony whereof we aflix' our signatt'lres.

DR. FRIEDRICH SASS. JOHANNES RADLOFF. J OHANN GERSTMAYR. 

